Cooling device for cooling medium-voltage apparatus using insulated heat pipes

ABSTRACT

The cooling device is suitable for fitting to existing installations, without redesigning them. It consists in using heat pipes ( 12 ) that are partly embedded in the casing ( 10 ) of the apparatus. This embedded portion ( 12 A) of the heat pipe ( 12 ) penetrating into the casing ( 10 ) has a sleeve ( 14 ) that is both electrically insulating and a good conductor of heat. The device is for application to circuit breakers in a medium-voltage, high-amperage electrical installation.

FIELD OF THE INVENTION AND DEFINITION

The invention relates in particular to the field of circuit breakers or disconnectors for medium-voltage generators, placed in a protective sheath, and using cooling devices called “heat pipes” that operate with a phase-change heat-transfer fluid.

It should be recalled that a heat pipe is presented in the form of a long hermetically-sealed enclosure containing a fluid with its gaseous phase and its liquid phase in equilibrium, in the absence of any other gas, ignoring traces.

DEFINITION

Heat pipe: Thermal apparatus in the form of a long hermetically-sealed enclosure containing a fluid with its gaseous phase and its liquid phase in equilibrium. Heat is transferred from the hot portion to the cold portion of the tube by vaporizing the liquid phase and condensing the vapor in the cold portion.

PRIOR ART AND PROBLEM POSED

The constant concern of makers of that type of equipment is to increase the ability of such apparatuses to conduct higher and higher currents, in particular for circuit breakers and disconnectors placed inside busbars at the outlets of power stations for producing or distributing electricity. That applies particularly for alternator circuit breakers.

A method that is generally used consists in making more uniform the temperature of the air that is in contact with the various heating and heated parts of the circuit breaker concerned. The cooling inside such a protective sheath may take place by natural or forced convection of the air enclosed therein and in which the circuit breaker is to be found, the prevailing temperature inside the protective sheath being considerably higher than the prevailing temperature outside, by 30° C. to at least 40° C.

Another solution consists in providing an increase in the current flow section in the various transmission elements, and thus increasing the size of circuit breaker parts.

Patent document EP 1 657 731 describes a known cooling device and method for cooling a high-voltage disconnector or a circuit breaker. FIG. 1 shows, in section, an embodiment described in that document. FIG. 1 mainly shows a medium-voltage conductor 2 or the casing of a circuit breaker. It is surrounded by evaporators 3 forming part of a cooling assembly 1 therefor. Such an assembly is accompanied by an insulating sleeve 7 surrounding a device operating with a phase-change heat-transfer fluid 5 in order to evacuate the heat collected by the evaporators 3. A flexible sleeve 9 completes the assembly. The various parts are placed together inside a protective sheath 8. The cooling assembly opens out to the top of this protective sheath 8 leading to a condensation device 4, e.g. with fins.

The object of the invention is to propose a different solution for this type of device.

SUMMARY OF THE INVENTION

To this end, the invention mainly provides a cooling device using phase-change heat-transfer fluids for medium-voltage apparatus and comprising at least one heat pipe.

According to the invention the heat pipe(s) is/are placed in such a manner as to penetrate in part into the apparatus and is/are electrically insulated, in this embedded portion, by means of a sleeve that is both electrically insulating and a good conductor of heat.

In a first possible embodiment of the invention, the sleeve is made of sintered aluminium nitride.

In a second embodiment, the sleeve is made of sintered boron nitride.

Preferably, the outside portion of the heat pipe(s) riot penetrating into the apparatus terminating at a condenser is provided with an electrically insulating sleeve.

Each heat pipe may possess an electrically insulating ring on an outside portion of the electrically insulating sleeve.

In addition, each heat pipe may possess an electrically insulating sleeve on its outside portion.

LIST OF FIGURES

The invention and its various technical characteristics can be better understood on reading the following description of three embodiments of the invention. The description is accompanied by six figures in which, respectively:

FIG. 1 shows a prior art cooling device;

FIG. 2, partially in section, shows the technology used in the device of the invention;

FIGS. 3A, 3B and 3C are cross-sections showing three embodiments of the invention; and

FIG. 4 is a longitudinal section showing the device of the invention, in particular that shown in FIG. 3C.

DETAILED DESCRIPTION OF THREE EMBODIMENTS OF THE INVENTION

FIG. 1 shows a portion of the casing 10 of a circuit breaker, the casing having a certain thickness in which the heat due to the flow of electricity at medium and high voltage and amperage accumulates.

In FIG. 2, two heat pipes are shown penetrating in part into the casing 10 of the circuit breaker.

In FIG. 2, the portion 12A of the heat pipe that is embedded in the casing 10 of the circuit breaker is therefore heated. The fluid in the heat pipe 12 vaporizes when accumulating the energy. The gas is thus diffused inside the heat pipe 12 until it reaches the non-embedded, opposite end 12B, where it condenses. The embedded end 12A is surrounded by a sleeve that is both electrically insulating relative to the casing 10 of the circuit breaker and also a good conductor of heat. In particular, mention may be made of the use of sintered aluminum nitride or of sintered boron nitride in order to constitute the electrically insulating sleeves 14.

As shown by the heat pipe 12 on the left, the assembly may be completed by a ring made of electrically insulating material that surrounds the outside portion 14A of the electrically insulating sleeve in order to increase the creepage distance.

As shown by the heat pipe 12 on the left, the outside portion 12B may also possess a second electrically insulating sleeve 18 in order to increase the creepage distance.

With reference to FIG. 3A, a first embedment of such a principle in a circuit breaker 20 is shown. In FIG. 3, in a common vertical plane, two heat pipes 12 both have respective embedded portions 12A that penetrate into the casing of the circuit breaker 20. The end of the outside portion 12B of each of these heat pipes 12 is surrounded by a system of fins 26 in order to form a condenser 24 so as to enable the heat to dissipate outside the enclosure 22 in which the circuit breaker 20 is placed.

Generally the liquid returns by gravity, thereby leading the condenser 24 to be placed high up. If the inside of the heat pipe 12 is provided with channels, liquid return is accelerated by capillary force, and this also enables the condenser 24 to be placed lower down, while accepting a loss of efficiency.

In FIG. 3A, in vertical section, it should be observed that the circuit breaker may be placed on an insulating support 28. In addition, the condensers 24 are therefore placed on the roof of the enclosure 22.

Both heat pipes 12, shown in FIG. 3A, are implanted in the circuit breaker 20, in a slightly offset manner, one on each side, so that their outside ends are further apart from each other. Thus, they may reach condensers 24 that are placed relatively far apart on the enclosure 22.

FIG. 3B shows an embodiment with the same elements as the embodiment shown in FIG. 3A. However, a fan device 30 is provided above the enclosure 22 in order to promote the flow of air through the condensers 24, and more precisely to promote the flow of air between the fins 26 thereof.

FIG. 3C shows a third embodiment that makes use of a third heat pipe 42A, placed between the two laterally offset heat pipes 42B.

In the embodiment of FIG. 3C, each heat pipe 42A, 42B terminates in at least one condenser 24.

FIG. 4 is a longitudinal section showing the manner in which the heat pipes 42A, 42B may be implanted at various points along a circuit breaker 20, or on other switchgear 50 associated with circuit breakers 20 that are always placed inside an enclosure 22, such as busbar section isolators, for example. Each heat pipe 42A and 42B is always connected to a condenser 24 that is placed on the roof of the enclosure 22.

The addition of suitable materials on the inside walls of the heat pipes 12, 42A and 42B also makes it possible for the heat pipes to be implanted upside down, and this increases cooling potential.

The main advantage of such a device is that it adapts to various heat pipe and cooling element technologies that have already been tested, without needing to develop insulation methods that need to contain the cooling liquid. 

1. A cooling device using a phase-change heat-transfer fluid for medium-voltage apparatus, comprising: at least one heat pipe (12, 42A, 42B); the device being characterized in that the at least one heat pipe (12, 42A, 42B) penetrates in part into the apparatus and is electrically insulated in this embedded portion (12A) by means of a sleeve (14) that is both electrically insulating and a good conductor of heat.
 2. A device according to claim 1, characterized in that the electrically insulating sleeve (14) is made of sintered aluminum nitride.
 3. A device according to claim 1, characterized in that the electrically insulating sleeve (12, 42A, 42B) is made of sintered boron nitride.
 4. A device according to claim 1, the assembly being placed inside a sheath (22), the device being characterized in that the outside portion (12B) of the heat pipes (12, 42A, 42B) not penetrating into the apparatus terminating at the condensers (24) possesses an electrically insulating sleeve (18).
 5. A device according to claim 1, characterized in that each heat pipe (12) possesses an electrically insulating ring (16) placed on an outside portion (14A) of the electrically insulating sleeve (14).
 6. A device according to claim 1, characterized in that each heat pipe (12, 42A, 42B) possesses an electrically insulating sleeve (18) on its outside portion. 